262 NICKERSON. [VOL. I. 



In the rather small number of living or freshly killed Euro- 

 pean frogs which I have been able to examine in Leipzig, I 

 have found but one specimen of D. ovocaudatum, but the fact 

 is suggestive that that one was attached in the Eustachian 

 tube of Rana cscnlenta. That I have not found D. ovocauda- 

 tum under the tongue of American frogs may be due to acci- 

 dent or oversight. It seems, on the other hand, not improbable 

 that the failure of observers to find it in the Eustachian tubes 

 of the European frogs may be clue to the same cause. It 

 would not surprise me if future investigation should show that 

 it occurs as frequently in that position as under the tongue 

 where it has hitherto been observed. 



The abundance of this parasite seems to vary greatly from 

 year to year. In the spring of 1893 it was quite abundant in 

 the vicinity of Boston, perhaps as many as one out of every 

 three or four frogs used for laboratory dissection harboring 

 specimens of the worm. During the next two years, although 

 a careful watch was kept for them, not a single specimen was 

 found in the frogs similarly used, although they were collected 

 from the same locality and the number examined was larger. 

 A similar variation for the vicinity of Leipzig has been men- 

 tioned by Looss ('94). 



There are several points in the anatomy of this species upon 

 which previous writers are not in agreement. One of these 

 is the position of the ovary, which is stated by Sonsino to be 

 upon the left side ; Looss found it always upon the right side. 

 In an examination of ten worms with respect to this point, I 

 found that in nine cases the ovary was on the left side (as was 

 the case also in the single Leipzig specimen), in one upon the 

 right. In the same specimens the posterior testis was in seven 

 cases the left one, in three the right. Several other worms 

 had the testes so evenly placed that they could not be counted 

 in either of these lists. From this very small number of 

 observations it would appear that the variations in position of 

 ovary and testes are not strictly correlated. 



The egg capsules in this species are terminated at one end 

 by filaments which are described by Vulpian ('59), Creutzburg 

 ('90) and Looss as being from one to one and one-half times the 



